Re–Ni cathodes obtained by electrodeposition as a promising electrode material for hydrogen evolution reaction in alkaline solutions

Abstract

Re–Ni cathodes catalytic activity towards hydrogen evolution reaction (HER) in the solution of sodium hydroxide is studied. Re–Ni coatings were deposited onto the surface of a copper substrate from ammonium-citrate solutions in the galvanostatic regime. The obtained deposits were examined by the complex of modern physical methods, namely: XPS, XRD, and SEM with X-ray microanalyzer. It was established that the full reduction of nickel species occurs during electrodeposition, while rhenium species electroreduction is incomplete. The obtained electrolytic deposits contained a high amount of hydrogen sorbed by them during electrodeposition. The increase in rhenium content in Re–Ni deposits caused the increase in their catalytic activity towards HER that was accompanied by Tafel slope decreasing. Heat treatment at 450 °C in vacuum resulted in a decrease in catalytic activity towards HER. It was suggested that high catalytic activity towards HER is caused by rhenium oxides included in the Re–Ni coatings. Heat treatment results in rhenium oxides reduction by sorbed hydrogen that causes a decrease in catalytic activity towards HER.